How do you recover from being the pushover teacher?

I just began my first full year of teaching. I am 22 years old. Everyone has told me that the first year is the hardest, but I still have high hopes. Before this school year, I did a short term (6 week) teaching position in Memphis City Schools. This was an 8th grade position. I had 5 classes and my students had run off every other sub that they had had through out the year. the teacher quit after the 2nd day of school, so you can imagine a class of inner city students that had subs all school year. I came during the LAST 6 weeks of school, after state testing and everything. They had pretty bad behavior. I basically made it through these weeks not realizing that I was being too much of a friend to them. I was the only teacher that stayed with them until the end, but I had NO control what so ever. With my new position, I told myself that I would do better and I would have a better outcome. I made note of several mistakes I had made before.
I am a very nice and kind hearted person, so it took a lot for me to get a mean face.
My first day was perfect, I did not smile, they were afraid of what I could possibly do and knew I meant business. I had clear rules and poated them and reminded them of them. I was not able to hold off my smile after day 1, but they still knew I meant business. I honestly had the intention of staying this way, but as time went on, I began to love my students so much. I have 7th and 8th grade all female classes. My mean “act” worked for about 3 weeks. I began to get comfortable and be myself with the students, but still tried to ensure that they knew I meant business. These 2 things didn’t work too well together for me. I even had a student tell me that one of my classes was trying to run me over, so I was determined to fix it. We have a 4 step behavior plan on my team. I’ve given behaior assignments, called parents and even sent a few to the office. I don’t think those are big threats when several students keep showing certain behaviors after they’ve seen me punish another student for the same thing. Weekly, I try to start off better, but things keep going back. I feel like I am at the point where I have told them that they are going to do better and I am going to be harder too many times. I think I’ve become unbelievable. I feel like I don’t have enough classroom consequences and alternatives for my students when they misbehave. I want my discipline to stay in my classroom for the most part.
Where can I go from here. At this point my main problems in class are talking during my lecture or lesson, talking during my bell ringer that I clearly tell them to stay quiet during, and not turning in homework. There are others, but I worry that I will not be able to recover with so many problems already present. I know I’ll get a fresh start every year, but I want something to get better this school year. Can anyone give me any ideas to help improve my “current” classroom management.
I think empty threats have bitten me in the butt. I want to get my classes together.